1. Field of the Invention
The present invention relates generally to medical devices and, more particularly, to the determination of placement of a medical device.
2. Description of the Related Art
This section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present invention, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present invention. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
In the field of medicine, doctors often desire to monitor certain physiological characteristics of their patients. For example, to measure certain characteristics, a non-invasive sensor may be utilized that transmits electromagnetic radiation, such as light, through a patient's tissue and then photo-electrically detects the absorption and scattering of the transmitted or reflected light in such tissue. The physiological characteristics of interest may then be calculated based upon the amount of light absorbed and/or scattered or based upon changes in the amount of light absorbed and/or scattered. In such measurement approaches, the light passed through the tissue is typically selected to be of one or more wavelengths that may be absorbed and/or scattered by one or more constituents of the blood or tissue in an amount correlative to the amount of the constituents present in the blood or tissue. In this manner, the measured amount of light absorbed and/or scattered may then be used to estimate the amount of blood or tissue constituent in the tissue using various algorithms.
One technique for monitoring the physiological characteristics of a patient is commonly referred to as pulse oximetry, and devices built based upon pulse oximetry techniques are commonly referred to as pulse oximeters. Pulse oximetry may be used to measure various blood flow characteristics, such as the blood-oxygen saturation of hemoglobin in arterial blood, the volume of individual blood pulsation supplying the tissue, and/or the rate of blood pulsations corresponding to each heart beat of a patient. Such physiological information allows doctors and other health care personnel to provide the best possible health care for their patients.
In processing a signal received by a pulse oximeter sensor, or any other non-invasive sensor utilizing similar data acquisition principles, the quality of the signal is typically dependent on the sensor making proper contact with the tissue. The sensor may be misplaced on the patient, or jostled or bumped, thereby affecting the contact of the sensor with the patient's tissue. In such instances, or in other circumstances where there may be poor contact between the sensor and the skin, light that otherwise might provide useful information may escape to the environment and never be detected or it may reach the light detection mechanism without passing through the patient's tissue, effectively providing no physiological information while reducing signal quality. Such lost or degraded information regarding the physiological characteristic, such as blood oxygen saturation, may result in an inaccurate indication of the patient's condition being provided to a health care provider.